Currently Being ModeratedApr 30, 2012 12:43 PM (in response to lukescott)
Insert the first disk, restart with the Option key held down, tab to it, press Enter, and use the Reset Password function. This won't affect your files, but they should be backed up anyway.
Currently Being ModeratedApr 30, 2012 2:57 PM (in response to lukescott)
Put your install DVD into the optical drive and reboot. As soon as you hear the boot chime, hold down the "c" key on your keyboard (or the Option key until the Install Disk shows up) until the apple shows up. That will force your MacBook to boot from the install DVD in the optical drive.
When it does start up, you'll see a panel asking you to choose your language. Choose your language and press the Return key on your keyboard once. It will then present you with an Installation window. Completely ignore this window and click on Utilities in the top menu and scroll down to Reset Password. After resetting the password use Startup Disk from the same menu to choose your hard drive for startup and restart.